For the pickled onions combine vinegar, sugar and 1 cup of water in a small saucepan and simmer red onions for about 10 minutes. Let chill in the refrigerator for about 20 minutes.

Spread a generous amount of aioli on the bottom bun. Place burger on top of the bottom bun and garnish it with desired amount of piquillo peppers, pickled onion and cilantro. Try adding your favorite hot sauce!